Use originalMaxAge

[rclmenezes]

Fixes https://github.com/fastify/session/issues/126

This PR is ready for review after https://github.com/fastify/session/pull/149 is merged. It adds one commit.

Checklist

• [ ] run npm run test and npm run benchmark
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added
• [ ] commit message and code follows the Developer's Certification of Origin and the Code of conduct

[Eomm]

#149 has been merged :+1:

[Uzlopak]

Thank you for the PR. I copied the relevant pieces to #162.

Closing in favor of #162